The present invention relates to a grinding tool, and particularly to one provided with two spaced grinding discs for simultaneously cutting two spaced grooves. The invention also relates to a spacer assembly which may be used with existing grinding tools having but a single grinding disc, to convert the grinding tool to one capable of simultaneously cutting two spaced grooves.
The invention is particularly useful with respect to grinding tools for cutting grooves in concrete walls in order to accommodate pipes or conduits passing through the walls. When the grinding tool is used for this purpose, it cuts two spaced grooves in the concrete wall, and the space between the grooves is then chiselled out in order to define a larger groove for accommodating the pipe or conduit.
One known form of grinding tool used for this purpose includes a grinding disc which cuts a single groove at one time. When using this type of tool, however, the two grooves must be cut separately, which substantially increases the time required for performing this operation.
Another type of grinding tool is also known including two grinding discs in spaced relation and adapted to simultaneously cut two spaced grooves, but such a known tool is substantially more complicated in construction, and therefore more expensive, than the single-disc grinding tool mentioned above.
An object of the present invention is to provide a grinding tool of relatively simple construction adapted to simultaneously cut two spaced grooves. Another object of the invention is to provide a spacer assembly which may be used with the existing single-disc grinding tools to convert such a tool for simultaneously cutting two spaced grooves.
According to one aspect of the present invention, there is provided a grinding tool comprising a rotary motor driving a rotary drive shaft; a first grinding disc having a center opening for receiving said drive shaft with the outer end of the drive shaft projecting through the opening in the grinding disc; a spacer assembly having a socket at one end receiving the projecting end of said drive shaft, a pin at the opposite end, and spacer means between said socket and pin; a second grinding disc having a center opening for receiving said pin of the spacer assembly with the outer end of the pin projecting through the latter opening; and an outer collar attached to said projecting end of the pin for securing the two grinding discs to the drive shaft in spaced apart relationship such as to enable the grinding tool to cut two spaced grooves.
According to another aspect of the invention, there is provided a spacer assembly for use with a grinding tool comprising: a rotary motor driving a rotary drive shaft, a first grinding disc having a center opening for receiving the drive shaft with the outer end of the drive shaft projecting through the opening in the grinding disc, and an outer collar attached to the projecting end of the pin for securing the grinding disc to the drive shaft. The spacer assembly comprises a socket at one end receiving the projecting end of the drive shaft, a pin at the opposite end, and spacer means between the socket and pin. The socket is adapted to project through the opening of the first grinding disc to thereby enable the spacer assembly to receive a second grinding disc having a center opening receiving the pin with the outer end of the pin projecting through the latter opening, whereby the outer collar may be attached to the projecting end of the pin to secure the two grinding discs to the drive shaft in spaced apart relation, and thereby to enable the grinding tool to simultaneously cut two spaced grooves.
According to preferred features in the preferred embodiment of the invention described below, the spacer assembly comprises a first spacer washer fixed at the socket end of the spacer assembly to bear against the first grinding disc; and a second spacer washer fixed at the pin end of the spacer assembly to bear against the second grinding disc.
According to a still further feature in the described preferred embodiments, the spacer assembly may further comprise one or more additional washers received over the pin between the second washer and the second grinding disc, to further space the second grinding disc from the first grinding disc.
It will thus be seen that the invention may be embodied in either a grinding tool constructed to have two grinding discs, or in a spacer assembly for converting existing single-disc grinding tools to two disc grinding tools, to enable two grooves to be simultaneously cut.
Further features and advantages of the invention will be apparent from the description below.